Studies of iron metabolism will be continued in at least three inherited hypochromic anemias of animals; in the mouse, sex-linked anemia (sla) and microcytic anemia (mk), and Belgrade anemia of the the rat (b). Specific experimental approaches include measurements of intestinal iron absorption in vivo and in vitro, especially in sla and mk anemias, and studies of subfractions of mucosal cells. Investigation of iron uptake by other cells, including isolated liver cells, will also be pursued to elucidate processes by which iron enters cells. Since newborn sla mice are anemic and may be iron deficient, investigation of iron metabolism by the placenta and fetus will also be carried out. In Belgrade anemic rats, studies of hemoglobin synthesis in vitro, and of the pathophysiology of the anemia in vivo will be started.